But total pay rose thanks to a 58% rise in share-based long-term incentives.

And over the past ten years, the median total earnings of a FTSE 100 chief executive has gone up by 243%, Steve Tatton, editor of IDS's directors' pay report, told the BBC.

Mr Tatton said the survey illustrated the "complex make-up of boardroom remuneration".

"With nearly two-thirds of FTSE directors benefiting from an LTIP [long-term incentive plan] award in the latest year, the higher share-based payouts clearly made up for any ground lost in lower annual bonuses," he added.

A director is typically awarded a proportion of their salary in shares, which pay out only if the director hits their performance targets.

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Media captionEarnings campaigner Luke Hildyard says: "The super rich are taking a bigger share of the UK's total wealth"

Mr Tatton told the BBC that the long-term incentive plans were generally awarded three years in advance, with the results from this survey reflecting decisions made in the 2009-2010 financial year when share prices were much lower.

He said the reverse was now likely to be happening, "with directors being granted fewer shares under that type of formula."

TUC general secretary Frances O'Grady said the survey's findings meant that top bosses' pay was growing 20 times faster than that of the average worker.

"It's one thing replacing bonuses with long-term incentive plans, but FTSE 100 companies are simply exploiting this change to make their fat cats even fatter," she said.